Method of making milling-cutters



F. MULLER.

METHOD OF MAKING MILLING CUTTERS.

APPLICATION HLED DEC.26, 1918.

1,348,299. at ted Aug. 3, 1920.

2 SHEETSSHEET 1. FL?" A 3 m we mfoz 51AM MW to may F. MULLER.

METHOD OF MAKING MILLING CUTTERS.

APPLICATION FILED DEC.26, 1918.

Patented Aug. 3, 1920.

2 SHEETSSHEET 2.

5 wuewtoz HATENT' OFFICE.

UNITED STATES rmmmmcn alumna, or marrow, CONNECTICUT, 'assiema To run ewnmr COMPANY, 'OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

mt'rnon or ataxme MILLING-CUTTERS.

To all whom it may concern:

Be it known that I, FRIEDERICH Momma, a citizen of the United States, residing at Hartford, in the county of Hartford and State ,of Connecticut, have invented certain new and useful Improvements in Methods of Making Milling-Cutters, of which the following is a speclfication.

It is a well known principle in the art of cuttingmetals that the cutting edge of the tool should preferably be inclined with respect to the direction of relative movement so as to effect a shearing cut. This inclination is of advantage in that it improves the cutting action and it is also of advantage in that it permits the tool to engage the work gradually and with relatively little shock instead of engaging it suddenly with reater shock. This principle has been app ied to relieved milling cutters which are of uniform diameter throughout and has also been applied to milling cutters havin a uniform taper from one end to the ot er. These milling cutters have their cutting edges longitudinally inclined with respect to the axis, the cutting edge usually approximately conforming to a helix. Thus each tooth is enabled to engage the work gradually and to effect a shearing cut.

I have applied this principle to accurately made and profierly relieved formed or contour cutters. y a formed or contour cutter I mean o'nein which the diameter varies from end to end in ways differing from a uniform taper, the cutting being thus adapted to cut a redetermined contour other than a straight ine. Prior to m invention it had not been deemed practica or possible to make such cutters with inclined cutting faces. The said invention is presented and claimed in my copending application for milling cutters, Serial No. 268,349, filed on even date herewith.

In my copending application for methods of making milling cutters, Serial No. 268,350, filed on even date herewith, I have presented a method of making cutters embodying the invention presented in In said application, Serial No. 268,349, and have also shown several variations of the said method or alternate ways of practisingit. In the present application I set forth and specifically claim one of the alternate forms of the said method presented in my application Serial No. 268,350. The method herein Specification of Letter: latent.

Patented Aug. a, 1920.

Application fled December 88.1918. leriel No. 268.358.

,set forth in undersome circumstances prefing drawings a cutter embodying the invention set forth in the aforesaid application Serial No. 268,349. It will be understood, however, that the drawings are for illustrative purposes only and are not to be conatrued as defining or limiting the scope of the invention, the accompanying claims bemg relied upon for that purpose. It will be particularly understood that the contour of the cutter shown has been selected merely by way of example and that any practical contour may be substituted for that illustrated.

Of the drawings: Figures 1 and2 are plan and end views respectively of a formed milling cutter such as may be made in accordance with the in- I vention.

Figs. 3 and 4 are enlarged fragmentary diagrammatic plan and end views res ectively of the milling cutter shown in igs. 1 and 2. In these views there is shown a smaller number of teeth and the inclination of the cutting faces and the relief are increased in order'to bring out the principles of the invention more clearly.

Fig. 5 is a diagrammatic view illustrating certain features of the cutter shown in Figs. 3 and 4.

Figs. 6 and 7 are side and plan views re spectively of a lathe tool which may be used for cutting the final milling cutter shown in F i 1 and 2.

igs. 8 and 9 are side and plan views respectively of an intermediate tool which may be used for making the lathe tool shown in Figs. 6 and 7.

Figs. 10 and 11 are side and plan views respectively of a preliminary reciprocatory cutter or tool which may be used for cutting the intermediate tool shown in Figs. 8 and 9.

Figs. 12 and 13 are enlarged diagrammatic side and end views respectively of the re-- 'ciprocable cutter shown in Figs. 10 and 11.

trating certain features of the tool shown in Figs. 12 and 13.

, Fi 15 is a plan view of the intermediate tool on the same scale as Fig. 12.

s Fig. 16 is an enlarged diagrammatic side view illustratin use for cutting t e lathe tool.

Fig. 17 is a plan view of the lathe tool on the same scale as Fig. 16.

10 Fig. 18 is an enlarged diagrammatic side view illustrating the lathe tool in use for cutting a final milling cutteg.

' Figs. 19 and 20 are enl rged. diagrammatic side and end views respectively of a 16 preliminary tool difl'erin somewhat from that shown in Figs. 12 an 13.

In order that the method may be clearl understood I will first describe a cutter suc as can be made in accordance with the invention. Referring particularly to Figs. 1 to 5 of the drawings, it will, be seen that I have shown a cutter A which is shaped to cut a a straight line. The cutter is provided with a plurality of generally longitudinal teeth 1 between which are grooves 2, the teeth and rooves being preferably spaced uniformly.

he grooves 2 between the teeth can be of any usual or referred depth and shape, as required by t e spacing and by the de th of the contour to be cut. The front wal 3 of each tooth 1 constitutes the cutting face thereof and this cutting face is radial or approximately so in order to provide a satisfactory cutting angle. Each cutting face 3 is inclined or positioned obliquely so that its longitudinal lines lie at angles to the axis of the cutter. Preferably, each tooth 1 is generally helical in form and each cut ting face 3 conforms to a helicoid. As illustrated, the helicoid is one formed by a generatrix following the axis of the cutter and also following a helix on a cylinder concentric with the axis thereof, the helicoid in this case being radial. The teeth and the cutting faces may be inclinedin either direction and the degree of inclination may be varied as required.

The cutter may be made for cutting. any so desired practical contour. The contour may be made up of a series of straight lines, or a series of circular arcs, or a combination of circular arcs and straight lines, or the contour may consist in whole or in part of non-circular curves. The cutter shown is adapted for cutting a contour consisting of straight end portions and a convex central ortion conforming to a circular arc and having a height I). It will be understood so that this particular contour has been selected merely by way of example and that the contour can vary in any practical way that may be desired, the method being particularly applicable however for making a s5 cutter havinga curved contour.

the intermediate tool inupon an axlal redetermined contour differing from The outer edge of. each cutting face 3 has I an outline which is adapted to cut the predetermined contour when the cutter is rotated, this outline of the cutting facefollowing the helicoidal surface thereof. 'In 10 other words the outer cutting edge of each face is of such form that the projectionof the said edge about the axis of the cutter lane of intersection is the same as the pre etermined contour to be cut. Th1s .will be more clearly understood from the diagrammatic views in Figs. 3 and 4. For the particular contour illustrated, the four points 4, 5, 7 and 8 on the outline of the cutting face are all at equal distances from the axis of the cutter; the central point 6 is at a distance from the axiswhich 1s less by the distance I) and all other points along the outline are at their respective correct distances from the center so that when the cutter is rotated they will define the correct predetermined contour, as shown by full lines in Fig. 5. This relationshi of the several points along the outline o the cuttin face obtains notwithstanding the fact t atthe cutting face is a warped or helicoidal surface.

- Each tooth of the cutter is relieved along lines 9 extending backward and inward from the outline of the cutting face, these relief lines forming a continuous surface or continuous surfaces which extend from end to end of the cutter. lThe relief lines are properly constructed notwithstanding the variations in radius at different points along the said outline and notwithstanding the variations in angular position resulting from the warped or helicoidal cutting face. Preferably the relief lines 9 are maintained in similar relationship to each other as they extend backward and inward, the lines con-' forming to spirals of Archimedes. The result is that each tooth of the cutter, at any axial plane of intersection, such as 5-5, has a distorted sha e, as shown b dotted lines in Fig. 5. his distorted s ape includes points 14, 15, 16, ,17 and 18 corresponding respectively to the points 4, 5, 6,7 and 8 on the outline of the cutting face. The distortion of shape results from the III fact that the successive inward inclined relief lines 9 start at different angular positions because of the inclined or helicoidal cutting face. Therefore with the cutting face inclined in the direction illustrated the 120 several points 17, 16, 15 and 14 to the left of the point 8 or 18 are spaced inward from the respective points 7, 6, 5 and 4 by pro gressively increasing distances. Notwithstanding this distortion in shape at an axial 126 plane of intersection, the outline or efl'ective contour at the cutting face is correct, as before stated.

When the relief lines 9 conform to spirals and are maintained in similar relationship 13.

. amazon as they extend backward and inward, as is preferred, it is possible to shar en or grind the teeth of the cutter on the ront cutting faces 3 without changing the effective consuch as -0, bac of'an initial cutting face cutter may angular advance is represented by e.

3 and similar to the said face, the same effe'ctive contour will be found. Therefore if the teeth are ground on their front faces to helicoids which are the same as the helicoids of the initial cutting faces the effective con tour will remain the same.

Ea'chcutting face of the cutter A has a certain degree of inclination which is represented by the ratio between a unit of length measured parallelly with the axis and longitudinally of the contgur and the angular advance of the cuyaing face corresponding to the said unit of length. For different cutters the actual angles of inclination with respect to the axis may differ vbecause of different diameters but the degree of inclination as defined above, ma remain the same. For the cutter A as ilustrated in Figs. 3 and 4 the: length d of the be taken as the unit of len h, 1 be seen that the correspon ing The actual linear advance of one end of the cutting face with respect to the other is represented in Fig. 4 by Each tooth of the cutter A has a certain degree of relief which is represented by the and it wi I ratio between the angular advance of the cutter and the corresponding decrease in radius. In'the case of spiral relief, the relief lines for the same degree of relief must always conform to similar spirals constructed about the center. For different cutters the actual angles of relief may differ because of different diameters but the degree of relief, as defined above, may remain the same. For any angle such as g of the cutter A the decrease in radius or the amount of clearance, is h. The relief lines 9 meet the circuferential lines at an angle such as 2'.

Taking up now the method of making the milling cutter, it will be understood that the preliminary steps of turning the blank, cutting the grooves therein, etc., can be carried on in any usual or preferred way, these not of themselves constituting any art of the present 'invention. The invention relates particularly to the method of shapin the blank to provide a distorted shape whicfi will enable it to cut a correct contour.

In accordance with the general method set forth in m aforesaid copending application, Serial o. 268,350, the shape of the cutter to be made is formed by means of a preliminary cutter which may be either a milling cutter or a reciprocatory tool. As set forth in the said application Serial No. 268,350 and as set forth and also claimed in my copending application for method of making milling cutters, SerialNo. 268,352, filedon even date herewith, the preliminary cutter, whether a milling cutter or a reciprocable tool, may be used to form a lathe tool adapted to cut the al cutter. The present application relates specifically to the method involving the use of the reciprocable preliminary cutter.

Fi s. 6 and 7 show a lathe tool X such as may used for cutting the final cutter A; Figs. 8 and 9 show an intermediate tool W such as may be used for cutting the lathe tool, and Figs. 10 and 11 show areciprocable preliminary cutter Y such as ma be used for making the intermediate tool The tool Y is adapted to be reciprocated along straight lines, as indicated by the vertical arrow in Fig. .12. At a plane such as 1414 transverse to the lines of reciprocation, the tool has a shape which is the same as the predetermined contour to be cut by the final cutter A. This is shown by dotted lines in Fig. 14 in which the points 4, 5 6 7, and 8 correspond respectively to the points 4, 5, 6, 7 and 8 of the cutter A, as shown in Fig. 5. The to face 19 of the tool is inclined, a shown in Fig. 13. The front face 20 of the tool is also beveled or inclined, as shown in Fig. 12, to provide the re uired relief.

he top face 19 of thetool Y has a degree of inclination which bears a predetermined ratio to the degree of inclination of the cutting face of eaclrtooth of the final cutter A. Inthe case of a reciprocable tool, the degree of inclination is represented by the rat1o between a unit of length measured longitudinally of the contour and transversely of the lines of movement and the amount of rise corresponding to the said unit of len th and measured, parallelly with the lines o movement. Any convenient degree of inclination may be selected butI have shown a degree of relief the same as that of the cutter A. Taking the Width d of the tool as the unit of length it will be seen that the corresponding amount of rise is f, which is the same as the advance or rise for the cutter A- at the outside radius thereof.

The front face 20 has a degree of relief which bears a predeterminedratio to the degree of relief of the final cutter. In the case of a reciprocable tool, the degree of relief is represented by the ratio between a unit of length measured parallelly with the lines of movement and the correspondin amount of clearance. If the degree of relief is the same as for the final cutter, as shown, the degree of relief is also the same. Inasmuch as the rise f for the tool Y is the same as the advance or rise for the cutter'A at the outside radius, the front face is given an amount of clearance which is the same as that of the cutter A at the outside radius thereof. In other words the tool is given a Fig. 14. This distorted contour has points 14, 15, 16, 17, and 18, all points 17, 16, 15 and 14 beyond the point 8 or 18 being spaced outward from the res ectively corresponding points 7, 6, 5 an 4 by pro res sively increasing distances. Inasmuc as the preliminary tool Y is provided with an inclined cutting face havin the same deree of inclination as the he icoidal cutting aces of the teeth of the final cutter A and is provided with the same degree of relief as the teeth of the final cutter the extent of distortion is the same as that of the cutter A at an axial plane of intersection.

The preliminary cutter Y is used to cut the intermediate tool W, as shown in Fig. 12, providing the said tool at its cuttin face 21 with a distorted contour which is the same, as the effective contour of the cutter Y shown by full lines in Fig. 14. This distorted contour is illustrated 1n the plan view in Fig. 15, the contour havingpoints 14", 15", 16", 17' and 18 corresponding respectively to the points 14, 15, 16, 17 and 18 of-the effective contour of the cutter Y. It will be observed that the tool W is formed without relief, it being fed perpendicularly to its cutting face 21, as indicated by the arrow in Fig. 12.

The intermediate tool W is used, as shown in Fi 16, for cutting a lathe tool X. The tool has a cutting face 22 and has its front face 23 inclined with respect to the cutting face to provide the necessary relief. The tool W is set with its cuttin face 21 arallel with the cutting face 22 o the tool X, and relative reciprocation is then effected along lines parallel with the front face 23. The result is that the cutting face'22 is formed with a distorted contour which is exactly the same as the distorted contour of the face 21 of the tool W. This distorted contour is shown in Fig. 17 and it has points 14", 15", 16", 17 and 18 corresponding respectively to the points 14", 15", 16", 17 and 18" of the cutter W.

Fig. 18 shows the tool X being used for shaping the cutter A. It will be understood that the blank is rotated as indicated by the arrow and that the tool X is moved inward and outward in timed relation to the rotation to provide relief. The distortion of the shape of the tool X is just sufficient to offset amp tool X to make a cutter having parts of its contour sharply inclined with respect to the axis and having the outer surface of each tooth extending backward toward the next following'tooth to an extent beyond that to which it could be cut by a preliminary shaped milling cutter. A cutter of this type is set forth in my copending application for milling cutters, Serial No. 368,928, filed March 26th, 1920.

. If preferred there can be variation from' the preliminary tool Y as shown in Figs. 12 and 13. The degree of inclination of the cuttin face can be increased or decreased as' desire and the degree of relief correspondingly decreased or increased. In Figs. 19 and 20 I have shown a tool Z similar to the tool Y but havin its top cutting face 24 provided with a egree of inclination onehalf that of the top cutting face 19 of the tool Y. The rise is j, which is one-half of the rise 7 of the cutter A. correspondingly the de ree of relief of the front face 25 is twice t at of the front face 20 of the tool Y. The clearance is is twice the clearance y of the tool Y, the angle Z being correspondingly greater than the angle 2'. As the result of the lesser inclination of the cuttin and the greater inclination of the ront face 25 the tool Z is given a distorted effective contour 14, 15', 16', 17 18', which is exactly the same as the effective contour 14, 15, 16, 17, 18, of the tool Y as shown by full lines in Fig. 14.

The tool Z is used to make the tool W, exactly as the tool Y is used, as shown in Fig. 16, the tool W being iven exactly the same contour. The tool V5 can then be used as before described, the subsequent steps being as shown in Figs. 16 to 18.

What I claim is:

1. The herein described method of shaping a relieved milling cutter adapted to cut a predetermined contour other than a straight line and having cutting faces inclined w1th respect to the axis, the method consisting in forming a reciprocable preliminary tool having the correct predetermined contour at planes of intersection transverse to the lines of cutting and provided with a cutting face with a degree of inclination bearin a predetermined ratio to the degree of inc ination of the cutting faces of the final cutter and provided with a degree of relief bearing a ratio to the degree of relief of the teeth of the final cutter which is the inverse of the face 24 ratio between the degrees of inclination, and

preliminary tool whereby the final cutter is formed with a distorted shape at axial planes of intersection but is adapted to cut the correct contour when rotated.

2. The herein described method of shaping a relieved milling cutter adapted to cut a predetermined contour other than a straight line and having cutting faces in clined with respect to the axis, the method consisting in forming a reciprocable preliminary tool having the correct predetermined contour at planes of intersection transverse to the lines of cutting and, provided with a cutting face with a degree of inclination bearing a predetermined ratio to the degree of inclination of the cutting faces of the final cutter and provided with a degree of relief bearing a ratio to the degree of relief of the teeth of the final cutter which is the inverse of the ratio between the degrees of inclination, in forming a lathe tool from the said preliminary tool, and in cutting the relieved final milling cutter by means of the said lathe tool whereby the final cutter is formed with a distorted shape at axial planes of intersection but is adapted to cut the correct contour when rotated.

3. The herein described method of shaping a relieved milling cutter adapted to cut a predetermined contour other than a straight line and having cutting faces inclined with respect to the axis, the method consisting in forming a reciprocable preliminary tool having the correct predetermined contour at planes of intersection transverse to the lines of cutting and provided with a cutting face with a degree of inclination the same as the de ree of inclination of the cutting faces of t e final cutter and provided with a de ree of relief the same as the degree of relief of the teeth of the final cutter, in forming a lathe tool from the said preliminary tool, and in cutting the relieved final milling cutter by means of the said lathe tool whereby the final cutter is formed with a distorted shape at axial planes of intersection but is ada ted to cut the correct contour when rotat 4. The herein described method of shaping a relieved milling cutter adapted to out a predetermined contour other than a straight line and having cutting faces inclined with respect to the axis, the method consisting in forming a reciprocable preliminary tool having the correct predetermined contour at planes of intersection transverse to the lines of cutting and provided with a cutting face with an angle of inclination the same as the angle of inclination of the cutting faces of the final cutter at the outside radius thereof and provided with a relief angle the same as the relief angle of the teeth of the final cutter at the outside radius thereof, in forming a lathe tool from the said preliminary tool, and in cutting the relieved final milling cutter by means of the said lathe tool whereby the final cutter is formed with a distorted shape at axial planes of intersection but is adapted to cut the correct contour when rotated.

5. The herein described method of shaping a relieved milling cutter adapted to cut a predetermined contour other than a straight line and having cutting faces inclined with respect to the axis, the method consisting in forming a reciprocable preliminary tool having the correct predetermined contour at planes of intersection transverse to the lines of cutting and provided with a cutting face with a degree of inclination bearing a predetermined ratio to the degree of inclination of the cutting faces of the final cutter and provided with a degree of relief bearing a ratio to the degree of relief of the teeth of the final cutter which is the inverse of the ratio between the degrees of inclination, in cutting an intermediate tool with the said preliminary tool, in cutting a lathe tool with the interme signature.

FRIEDERICH MULLER. 

